1. Field of the Invention
The present invention relates to a refrigerating apparatus used to air conditioners, refrigerators and the like, and more specifically, to a refrigerating apparatus using a mixed refrigerant which does not contain chlorine.
2. Description of the Prior Art
Conventionally, so-called hydrocarbon fluoride refrigerants containing chloride such as CFC, HCFC and such like are widely used as an operating fluid for a refrigerating cycle because they are a most suitable substance as a refrigerant due to their excellent thermodynamic property and stability.
As described in, for example, Japanese Patent Publication Laid-Open No. 3-63461, Japanese Patent Publication Laid-Open No. 59-84049, Japanese Patent Publication Laid-Open No. 5-172408 and the like, it is well known that refrigerating apparatuses using these refrigerants prevent the overheat of compressors and achieve a wide range of an operating pressure.
Hydrocarbon fluoride substances containing chloride are not decomposed due to their stability and reach the stratosphere by convection. It is found that since these substances are decomposed by strong ultraviolet rays in the sky and separate chlorine atoms which react with ozone, they have an action for destroying the ozone layer. It is determined to entirely abolish the hydrocarbon fluoride substances containing chloride to protect the ozone layer which has a function to cut off ultraviolet rays harmful to human bodies in the sky. Although HCFC-22 which is widely used as a refrigerant for air conditioners and refrigerators is also an object to be abolished, since it is less effective to the destruction of the ozone layer than CFCs designated as specific Freons, a longer period of grace is admitted to the substance. It is essential to develop replacement refrigerants and refrigerating apparatuses applicable to the replacement refrigerants in the period of grace.
At present, HFC-32, HFC-125, HFC-134a , HFC-143a, HFC-152a and such like, for example, as hydrocarbon fluoride refrigerants which do not contain chloride causing the destruction of the ozone layer are examined as new refrigerants to be replaced with conventional refrigerants such as HCF-C22 and such like and any one of them or a combination of a plurality of them is influential. Development is carried out aiming at a refrigerant having a performance factor such as a refrigerating capacity, efficiency and the like and a cyclic state such as an operating pressure, temperature and the like equivalent or near to those of conventional refrigerants. This is because that a caution is paid to permit the replacement refrigerants to be handled in the same manner as conventional refrigerants so that the new refrigerants can be employed with a minimum change of the specification of products and manufacturing apparatuses which have been applied to conventional refrigerants.
Incidentally, a compressor, cycle auxiliary components and a cycle control device must be arranged to comply with the new refrigerants so that a performance equivalent to that of conventional products is maintained and a cycle state such as a range of an operating pressure, temperature and the like is stabilized at all times. Further, when different refrigerants are used, refrigerator oils must be also changed to comply with the new different refrigerants. That is, although chlorine has a function for assisting compatibility with oil, new refrigerants do not contain chloride causing the destruction of the ozone layer as described above. Thus, the compatibility of the new refrigerants with conventional refrigerator oils, which are mainly composed of mineral oils, alkylbenzene and such like and have been widely used to conventional refrigerants, is greatly lowered and thus the new refrigerants cannot be used with the conventional refrigerator oils. To cope with this problem, there is developed new refrigerator oil which can secure the compatibility with the new refrigerant by the molecular polarity of ether and ester.
Incidentally, when conventional refrigerator oil and a chlorine substance contained in a conventional refrigerant are mixed in a refrigerating cycle to which a new refrigerant is applied, the new refrigerant and new refrigerator oil are chemically changed by the mixing of them, and, for example, a material used in the cooling cycle may be corroded by the occurrence of acid. Thus, a problem arises in that the reliability of products is greatly lowered.
An object of the present invention is to provide a refrigerating apparatus which can realize a cycle state such as a performance, operating pressure, temperature and the like which are equivalent to that of a conventional refrigerating apparatus using a new refrigerant and new refrigerator oil while securing the reliability of components without damaging the performance thereof.
To achieve the above object, a first feature of the present invention resides in an refrigerating apparatus constituting a refrigerating cycle by sequentially connecting a compressor, a condenser, a liquid receiver, an accumulator, an expansion valve and an evaporator, wherein a mixed refrigerant containing at least R-125 and R-143a is used as a refrigerant for the refrigerating cycle, ester oil and/or ether oil is used as refrigerator oil and a liquid injection type scroll compressor is used as the compressor.
A second feature of the present invention resides in that a triple-mixed refrigerant composed of 40-48 wt %, e.g., 44 wt % of R-125, 47-57 wt %, e.g., 52 wt % of R-143a and up to 10 wt %, e.g., 4 wt % of R-134a is used as a refrigerant for a refrigerating cycle, ester oil and/or ether oil is used as refrigerator oil and further a liquid injection type scroll compressor is used as a compressor.
An example of the liquid injection type scroll compressor is arranged such that the downstream side of the condenser is connected to the scroll compressor through a liquid injection piping, and means for controlling an amount of a liquid injection the compressor is provided in the liquid injection piping.
It is preferable that the refrigerator oil is mainly composed of ester oil of fatty acid and having a dynamic viscosity of 2-70 cSt at 40xc2x0 C. and 1-9 cSt at 100xc2x0 C. and at least two ester linkages in a molecule. Further, the condenser can be arranged as a heat exchanger whose piping has a diameter smaller than the refrigerant piping of a heat exchanger constituting the evaporator in order to increase a heat exchanging efficiency in the condenser. An electronic expansion valve disposed to the liquid injection piping is most suitable as the liquid injection amount control means and a controller is provided to adjust an amount of an injected liquid by controlling a degree of opening of the electronic expansion valve in response to a discharge side temperature of the compressor.
A third feature of the present invention resides in a refrigerating apparatus, which comprises a refrigerating cycle composed by sequentially connecting a scroll compressor, a condenser, a liquid receiver, an accumulator, an expansion valve and an evaporator, a triple-mixed refrigerant composed of 40-48 wt %, e.g., 44 wt % of R-125, 47-57 wt %, e.g., 52 wt % of R-143a and up to 10 wt %, e.g., 4 wt % of R-134a used as a refrigerant for the refrigerating cycle, refrigerator oil composed of ester oil and/or ether oil, a liquid injection piping connecting the downstream side of the condenser to the scroll compressor, means provided with the liquid injection piping for controlling an amount of a liquid injected into the compressor, a revolution-controllable motor for driving the scroll compressor, a blower for supplying external air to the condenser and a revolution-controllable motor for the blower, means for detecting a discharge temperature of the compressor, means for detecting a liquid temperature of the condenser, and means for detecting a temperature of intake air to the condenser, wherein the liquid injection amount control means and the motor of the blower are controlled according to values detected by the detecting means. It is preferable to provide a pressure controller which detects a pressure of the condenser and decreases, when the pressure reaches a preset high pressure value, a capacity of the compressor by decreasing revolutions of the compressor motor, whereas increases, when the pressure reaches a present low pressure value, a capacity of the compressor by increasing revolutions of the compressor motor. Further, it is effective that when a pressure reaches the preset high pressure value, the pressure controller decreases a high pressure by controlling revolutions of the blower motor to its full speed, whereas when the pressure reaches the preset low pressure value, the pressure controller increases the high pressure by decreasing revolutions of the blower motor.
A fourth feature of the present invention resides in a refrigerating apparatus, which comprises a refrigerating cycle composed by sequentially connecting a scroll compressor, a condenser, a liquid receiver, a dryer, an expansion valve, an evaporator, a strainer and an accumulator, a triple-mixed refrigerant composes of 40-48 wt %, e.g., 44 wt % of R-125, 47-57 wt %, e.g., 52 wt % of R-143a and up to 10 wt %, e.g., 4 wt % of R-134a used as a refrigerant of the refrigerating cycle, refrigerator oil composed of ester oil and/or ether oil, a liquid injection piping connecting the downstream side of the condenser to the scroll compressor, means provided with the liquid injection piping for controlling an amount of a liquid injected into the compressor, wherein a desiccating agent used for the dryer is composed of synthesized zeolite in which each of fine holes extending to molecule adsorbing cavities in a crystal structure has a diameter equal to or less than 3.3 angstroms which is smaller than a molecule of the hydrocarbon fluoride refrigerant which does not contain chloride and larger than a molecule of water.
A fifth feature of the present invention resides in that a double-mixed refrigerant composed of R-125 and R-143a, e.g., 50 wt % of R-125 and 50 wt % of R-143a, is used as a refrigerant for a refrigerating cycle, ester oil and/or ether oil is used as refrigerator oil and further a liquid injection type scroll compressor is used as a compressor.
Even the refrigerating apparatus using the above refrigerant can achieve an operating pressure, temperature and performance equivalent to those of a refrigerating apparatus using a conventional refrigerant by employing the liquid injection type scroll compressor.
That is, when an evaporating temperature is low, an amount of a refrigerant circulating in the refrigerating cycle is decreased and a temperature of a gas discharged from the compressor is increased. As a result, there is caused a danger that the promotor and the like may be seized, and the like. In the present invention, however, the compressor is prevented from being overheated and can be operated in a wide evaporating temperature by injecting a high pressure liquid refrigerant into the section side or intermediate compression chamber of the compressor through the pressure reduction unit.
A capillary system, an injection valve system, an electronic expansion valve system or a system combining them is employed as the liquid injection system so that a flow rate of an injected liquid can be made constant to keep a temperature of a discharged gas constant. As a result, a cycle can be stabilized and reliability can be secured.
Further, compatibility with the new refrigerant can be secured by the employment of the ester oil and/or ether oil as the new refrigerator oil, whereby the reliability and performance of components can be secured.
As described above, the present invention can realize the refrigerating apparatus whose capacity can be controlled in a wide range covering an evaporating temperature of the evaporator of xe2x88x9260xc2x0 C. to +5xc2x0 C. using the new refrigerant which does not contain chlorine causing the destruction of the ozone layer, without almost changing the arrangement of a conventional refrigerating apparatus.
Other features, objects and merits of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings.